(1) Field of the Invention
The present invention relates to a transistor module and a transistor driving module. More particularly, the invention relates to a transistor module and a transistor driving module with over current protection.
(2) Description of the Prior Art
FIG. 1 is a schematic diagram of a conventional buck converter. Referring to FIG. 1, the buck converter comprises a controller 10, a transistor switch 20 with an built-in driving circuit, an inductance L, an output capacitance C, and a voltage feedback circuit VD, to transfer an input voltage Vin into an output voltage Vout to drive a load Ld. The controller 10 receives a voltage feedback signal VFB which is generated by the voltage feedback circuit VD, and generates a pulse width modulation signal pwm.
The transistor switch 20 includes a pulse width control circuit 25, a high side driving circuit 30, a low side driving circuit 35, a high side transistor M1, and a low side transistor M2. The pulse width control circuit 25 receives the pulse width modulation signal pwm to the turn-on and turn-off the high side transistor M1 and the low side transistor M2 accordingly. Therefore, the power delivered by the input voltage Vin through the transistor switch 20 can be controlled and converted through the inductance L and the output capacitance C, such that the output voltage Vout is stabilized at a predetermined voltage value. In order to make the high side transistor M1 be turned-on and turned-off accurately, a bootstrap circuit could be added. The bootstrap circuit includes a diode D and a boost capacitance Cboot which are coupled in series between the input voltage Vin and the connecting point between the high side transistor M1 and the low side transistor M2. Thus, the bootstrap circuit can offer a potential, higher than a potential of the connecting point between the high side transistor M1 and the low side transistor M2 by a potential approximates the input voltage Vin, to the high side driving circuit 30. Therefore, the high side driving circuit 30 can accurately turn-on and turn-off the high side transistor M1.
The design of the transistor switch with built-in driving circuit makes the controller 10 need not to be coupled to the input voltage Vin so as to decrease the withstand voltage request. So, the cost of the controller 10 can be decreased. However, the controller 10 and the transistor switch 20 are two independent packages, such that a delay-time may exist between two independent packages. Due to that the controller 10 and transistor switch 20 are communicated by the pulse width modulation signal pwm. The controller 10 cannot understand the situations of the high side transistor M1 and the low side transistor M2 accurately, such that the high side transistor M1 and the low side transistor M2 are usually burned out because of the over current in the actual application.